The concentration of delta-9-tetrahydrocannabinol (THC) in cannabis may lead to platelet dysfunction, according to a study of nonhuman primates published ahead of print in the American Journal of Physiology-Cell Physiology.

Platelets, a component of blood, play a role in maintaining blood vessel (vascular) health and aid wound healing and placental development during pregnancy. 

An estimated 22 million people in the US use marijuana every month for recreational or medical purposes. The concentration of delta-9-tetrahydrocannabinol (THC) in cannabis products has increased over the years from less than 4% to more than 15% in 2018.

In the study, the research team explored the effects of THC on platelet function in rhesus macaque monkeys.

Male and female rhesus macaques were given a THC cookie each morning before breakfast. Over several months, the researchers incrementally increased the animals’ THC levels to approach standard by-weight dosages consistent with Colorado’s medical marijuana dose recommendations. The research team compared blood samples of the animals before and after the trial and found that THC reduced platelet aggregation—a step in the process of blood clot formation—and lowered production of thromboxane, a lipid involved in clotting. However, THC did not affect clotting times.

“Although marijuana has been used for the treatment of chronic pain, insomnia, nausea and vomiting, studies have also suggested that marijuana use is associated with cardiovascular system dysfunction, including both thrombosis and compromised vascular integrity in select cases,” wrote the researchers of a new study.

These results may call for “taking a thorough drug history for those undergoing surgery or are pregnant,” the researchers wrote. “Our observations may have important implications for clinical health policies regarding the use of medical marijuana in the future.”

cannabis platelet dysfunction